1. Field of the Invention
The invention relates to a method for testing vacuum packages.
2. Description of the Related Art
Vacuum packages are checked visually with regard to seal-tightness. Generally, in vacuum-sealed packages the packaging does not rest tightly against the article when the seal or welding seam is leaking. The packaging lifts off the article and is loose. Air can penetrate into the package, and this can cause the vacuum package to become unstable.
It is an object of the present invention to provide a method for testing vacuum packages that can be performed easily.
In accordance with the present invention, this is achieved in that the packaging is placed with at least one surface section against at least one contact surface of a vacuum device, wherein the vacuum device in operation produces a vacuum behind the contact surface, viewed in the flow direction; in that a parameter correlated with the air flow through the contact surface is measured; in that the parameter is compared with at least one limit value; and in that a first state is assigned to the vacuum package when surpassing the limit value and a second state is assigned to the vacuum package when dropping below the limit value.
When a vacuum package is intact, the packaging, usually a packaging film, rests tightly against the packaged article. When the vacuum package is damaged, the packaging film no longer rests tightly against the packaged article because via the damaged location of the packaging surrounding air can penetrate into the package. When the vacuum package is placed with a surface section against a contact surface of a vacuum device and a vacuum is generated by means of the vacuum device, the vacuum package is sucked against the contact surface of the vacuum. When the vacuum package is intact, intermediate spaces remain between the packaging and the contact surface of the vacuum device. When air can penetrate Into the package as a result of the packaging material being damaged, the packaging film is pulled or sucked against the contact surface of the vacuum device and closes the vacuum device to a great extent.
By measuring a parameter which is correlated with the air flow through the contact surface and comparing the parameter with at least one limit value, it is possible in a simple way to determine whether a package rests against the contact surface, whether the vacuum package is seal-tight, or whether air can penetrate into the package. A corresponding state is then assigned to the package.
The method requires no complex devices and can be performed with simple means. The method can be used for testing the seal-tightness of the package or for testing whether a package rests against the contact surface. Both tests can be performed at the same time when a comparison is carried out relative to several limit values.
Advantageously, the vacuum package has at least one partially profiled surface In the surface section while the contact surface is substantially planar. The profiled surface of the vacuum package enables performing of the method with a conventional vacuum device having a planar surface. The method can be performed also In the case of vacuum packages with a planar surface when the contact surface is expediently provided with a profiling.
Advantageously, the parameter is compared with a lower limit value. When the vacuum package is intact, the Intermediate spaces between the contact surface and the surface section remain intact. The air flow through the contact surface reaches a constant value when operating the vacuum device. When the vacuum package is damaged, the packaging material is pulled against the contact surface so that the intermediate space is reduced. The air flow through the contact surface is thus also reduced. When the air flow drops below a lower limit value, the vacuum package is damaged.
Advantageously, the parameter is compared with an upper limit value. When the air flow through the contact surface of the vacuum device is very large, no vacuum package rests against the contact surface.
Expediently, the parameter is selected to be the pressure downstream of the contact surface. The pressure downstream of the contact surface can be measured with simple means and allows to draw direct conclusions in regard to the air flow through the contact surface because the vacuum device produces a vacuum downstream of the contact surface. When the pressure downstream of the contact surface drops significantly, the air flow through the contact surface is minimal and the vacuum package is damaged. However, it can be expedient to measure as a parameter the course of the pressure. In particular In the case of small damaged areas of the vacuum package, the packaging is not immediately pulled against the contact surface upon applying the vacuum but will approach it slowly. The drop in pressure downstream of the contact surface indicates that the vacuum package is damaged because the pressure downstream of the contact surface has a constant level when the vacuum package is intact.
As a result of the required amount of time that elapses until the vacuum package rests completely against the contact surface, it is provided that the operating parameter is measured after a predetermined time has elapsed from the moment of placing the vacuum package onto the vacuum device. Expediently, the parameter Is measured in a vacuum chamber arranged downstream of the contact surface. Advantageously, the vacuum device is a suction gripping device with which the vacuum package is gripped. Such suction grippers are known in connection with robots and automated devices and can be integrated simply and inexpensively.
The method is carried out especially in combination with a transport step. When a suction device is used for the transport step, the method can be performed in already existing devices without additional expenditure. The time that is required for performing the transport step can simultaneously be used for testing the package. Based on the test result, the transport step can be advantageously controlled so that, for example, damaged packages can be directly removed. The transport step is carried out expediently by means of a handling robot.